Sunlight is typically regarded as unpolarized light. In order to reduce the glare on reflected light, glass lenses, and in particular sunglass lenses, have incorporated polarizing elements. The lens is typically polarized by introducing a polarization film to each sunglass lens element to produce double refraction wherein the impinging light is divided into two orthagonal beams by the polarizing lens elements.
Bigradient and single-gradient coatings have also been applied to sunglass lens elements in order to produce a mirrored appearance for the sunglass lenses and to decrease transmission of visible light in order to reduce the associated glare. See for example, Hutchings U.S. Pat. No. 2,409,356 and Barkely U.S. Pat. No. 2,675,740 which describe a coating for lens elements applied as a film on upper and lower portions of the lens elements by a high vacuum thermal evaporation process. Bigradient coatings have typically not been utilized, however, in combination with polarization films because the polarization films are destroyed by the heat required to apply the bigradient coating.
A sunglass lens element incorporating both a polarization film, a bigradient coating, and anti-reflectant coating is described in Richards et al. U.S. Pat. No. 4,838,673, entitled Polarized Lens and Method of Making the Same. The sunglass lens element of the Richards, et al., patent comprises a pair of ground mineral glass mounds laminated together with polarization film to form a single lens element. The outer surface of the first glass mound is thereinafter coated with a bigradient coating while the outer surface of the second glass mound is coated with an anti-reflectant coating.
The Richards, et al. patent also discloses a method for manufacturing such sunglass lens elements which includes the steps of positioning the laminated lens element on an inner dome of a vacuum vaporization dome. The lens elements, preferably at least one pair of right and left lenses, are aligned on the inner dome according to reference lines existing thereon, and bigradient materials are vaporized within the vacuum vaporization dome such that they adhere to the outer or convex surface of the lens element. A cooling means is also required for maintaining the inner dome at a temperature less than or equal to 50.degree. C. such that the polarization film is not destroyed. The vaporizing material is also blocked along the horizontal axis of the lens element, so as to establish a separate bigradient coating on the upper and lower surfaces of the lens element.
In conclusion, although sunglass lenses incorporating polarization films, a bigradient coating, and an anti-reflectant coating are highly desirable, the art has not heretofore suggested a viable sunglass lens incorporating a polarization film, a bigradient coating, and an anti-reflectant coating.